Comparative characterization of non-treated and UV-irradiated bilberry leaf extract-loaded liposomes: Physicochemical properties, stability, and antioxidant capacity

Vaccinium myrtillus L. (European bilberry) leaves are rich in phenolic acids, flavonoids, and anthocyanins. To improve the stability, bioavailability, and controlled release of these bioactives, bilberry leaf extract was encapsulated in liposomes using proliposome technology. The study compared non-treated and UV-irradiated liposomal systems, evaluating encapsulation efficiency (EE), FT-IR spectra, physical properties, and antioxidant activity. FT-IR results indicated that lipid bands dominated the spectra, masking extract-specific bands. Antioxidant activity remained stable post-UV treatment, with ABTS and DPPH inhibition values of 53.17% and 68.71%, respectively. Over a 60-day period, liposomes maintained narrow size distributions (5169.7–5508.7 nm), with zeta potential ranging from −5.02 mV to −9.16 mV and polydispersity index between 0.294–0.437. UV irradiation had a minimal impact on physicochemical or antioxidant characteristics. These findings highlight the potential of liposomal delivery systems for bilberry leaf extract in various applications, with an additional need to improve system stability, i.e., increase zeta potential.